In general, a cooling system of a vehicle controls rotation speed of a water pump based on a coolant temperature. The cooling system of the vehicle circulates the coolant circulating through a cooling load generating heat and a radiator discharging the heat to the outside via the water pump.
When driving the vehicle at a high altitude, as the atmospheric pressure is reduced, the water pump suction pressure is reduced. When the water pump suction pressure is reduced, as the water pump rotation speed is increased, the probability of cavitation is increased. The cavitation signifies a phenomenon in which the coolant is vaporized in an impeller of the water pump.
The probability of the cavitation is increased by increasing the water pump rotation speed, a flow rate of the coolant, and a water pump suction temperature, and reducing the water pump suction pressure and a saturation vapor pressure. If the atmospheric pressure is reduced, since the water pump suction pressure is reduced, the probability of the cavitation is increased.
Particularly, when comparing a fuel cell vehicle with a vehicle including an engine, there is a need for the increase in the coolant flow rate. However, an air-tightness level is low so that a pressure range capable of pressurizing is reduced, thus limiting the flow rate of the coolant to design a stable cooling system against a pressure variation of external air. Accordingly, there is a demand for a method of preventing the cavitation from being generated due to the variation in atmospheric pressure.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.